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Original question:

BQ76952: BQ76952 SDA Pin Pulled Low Unexpectedly

BQ76952: CC2 Current Reading

Vikram Jain
Prodigy 60 points
Part Number: BQ76952

Tool/software:

Dear Experts, 

I ma reading the CC2 value in 10mA resolution. We have measured the value on CAN and Scope. 

While the measured value on scope has 100Hz oscillation but the values reported by AFE are way too slow in reflecting the same. Below is the reference schematic diagram for SRN and SRP. 

 

We are using only 1 shunt resistor 0.5 miliohms and CCGain = 0x41723055 and CC Capacity = 0x4a89c74d

In the above image Blue signal is Current reported by CC2 and Green is filtered current using LPF. 

Above is the image of same current measured on the scope, the ripple that you see is 100Hz, but for some reason the same response on AFE reported CC2 values are are in seconds. I

I would like to have your expert advice on why this could be happening.  

  • 0
    TI__Genius 17835 points

    Hello Vikram,

    How often are you measuring the CC2 value? Are you only measuring the CC2 value when you do so? Also, what is your test procedure for this?

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Prodigy 60 points

    I read CC2 values only when FULLSCAN bit is set in alarm status. 

    There is a separate Task for reading CC2 (5ms task) values and Cell Voltages and Temperature (5ms task) .

    There is no test procedure, values are measured on Scope using Current probe and data reported on CAN  

  • 0 in reply to Vikram Jain
    TI__Genius 17835 points

    Hello Vikram,

    Are you measuring at the device pins? There are RC filters near the pins that could also alter your captured waveforms.

    FULLSCAN also takes ~189ms by default, therefore there is a high chance of aliasing occurring. You can turn on the ADC to be faster (~94ms), but it may be less accurate. The 0x3A CC2 Current() command will be useful instead if you choose to try that option. Section 4.3 Coulomb Counter and Digital Filters in the BQ76952 Technical Reference Manual may help with more information regarding it.

    Best Regards,
    Alexis